1,022 research outputs found
Affinity and Fluctuations in a Mesoscopic Noria
We exhibit the invariance of cycle affinities in finite state Markov
processes under various natural probabilistic constructions, for instance under
conditioning and under a new combinatorial construction that we call ``drag and
drop''. We show that cycle affinities have a natural probabilistic meaning
related to first passage non-equilibrium fluctuation relations that we
establish.Comment: 30 pages, 1 figur
A parity breaking Ising chain Hamiltonian as a Brownian motor
We consider the translationally invariant but parity (left-right symmetry)
breaking Ising chain Hamiltonian \begin{equation} {\cal H} = -U_2\sum_{k}
s_{k}s_{k+1} - U_3\sum_{k} s_{k}s_{k+1}s_{k+3} \nonumber \end{equation} and let
this system evolve by Kawasaki spin exchange dynamics. Monte Carlo simulations
show that perturbations forcing this system off equilibrium make it act as a
Brownian molecular motor which, in the lattice gas interpretation, transports
particles along the chain. We determine the particle current under various
different circumstances, in particular as a function of the ratio and
of the conserved magnetization . The symmetry of the term
in the Hamiltonian is discussedComment: 11 pages, 4 figure
The two-dimensional two-component plasma plus background on a sphere : Exact results
An exact solution is given for a two-dimensional model of a Coulomb gas, more
general than the previously solved ones. The system is made of a uniformly
charged background, positive particles, and negative particles, on the surface
of a sphere. At the special value of the reduced inverse
temperature, the classical equilibrium statistical mechanics is worked out~:
the correlations and the grand potential are calculated. The thermodynamic
limit is taken, and as it is approached the grand potential exhibits a
finite-size correction of the expected universal form.Comment: 23 pages, Plain Te
Granular Rough Sphere in a Low-Density Thermal Bath
We study the stationary state of a rough granular sphere immersed in a
thermal bath composed of point particles. When the center of mass of the sphere
is fixed the stationary angular velocity distribution is shown to be Gaussian
with an effective temperature lower than that of the bath. For a freely moving
rough sphere coupled to the thermostat via inelastic collisions we find a
condition under which the joint distribution of the translational and
rotational velocities is a product of Gaussian distributions with the same
effective temperature. In this rather unexpected case we derive a formula for
the stationary energy flow from the thermostat to the sphere in accordance with
Fourier law
Charge renormalization and other exact coupling corrections in the dipolar effective interaction in an electrolyte near a dielectric wall
The aim of the paper is to study the renormalizations of the charge and of
the screening length that appear in the large-distance behavior of the
effective pairwise interaction between two charges in a dilute electrolyte
solution, both along a dielectric wall and in the bulk. The electrolyte is
described by the primitive model in the framework of classical statistical
mechanics and the electrostatic response of the wall is characterized by its
dielectric constant.Comment: 60 pages 9 figure
Two-dimensional two-component plasma with adsorbing impurities
We study the behavior of the two-dimensional two-component plasma in the
presence of some adsorbing impurities. Using a solvable model, we find analytic
expressions for the thermodynamic properties of the plasma such as the -body
densities, the grand potential, and the pressure. We specialize in the case
where there are one or two adsorbing point impurities in the plasma, and in the
case where there are one or two parallel adsorbing lines. In the former case we
study the effective interaction between the impurities, due to the charge
redistribution around them. The latter case is a model for electrodes with
adsorbing sticky sites on their surface
New duality relation for the Discrete Gaussian SOS model on a torus
We construct a new duality for two-dimensional Discrete Gaussian models. It
is based on a known one-dimensional duality and on a mapping, implied by the
Chinese remainder theorem, between the sites of an torus and those
of a ring of sites. The duality holds for an arbitrary translation
invariant interaction potential between the height variables on
the torus. It leads to pairs of mutually dual potentials
and to a temperature inversion according to .
When is isotropic, duality renders an anisotropic
. This is the case, in particular, for the potential that is
dual to an isotropic nearest-neighbor potential. In the thermodynamic limit
this dual potential is shown to decay with distance according to an inverse
square law with a quadrupolar angular dependence. There is a single pair of
self-dual potentials . At the self-dual
temperature the height-height
correlation can be calculated explicitly; it is anisotropic and diverges
logarithmically with distance.Comment: 26 pages, 2 figure
Genèse et fonctionnement des sols en milieu équatorial
La genèse des sols en milieu équatorial présente une forte composante biologique. La structure générale des profils ferrallitiques s'explique par le recyclage biologique des principaux éléments intervenant dans les équilibres minéraux-solutions, et la plupart des minéraux secondaires des sols ferrallitiques sont en rééquilibrage constant avec les conditions du milieu. La genèse des podzols est liée à une exportation précoce des composés organo-métalliques formés dans les horizons de surface, dépendante de la dynamique de l'eau à l'échelle des systèmes. (Résumé d'auteur
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